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<h1><a href="../Table_of_Contents.html"><img src="../mpl_logo.jpg" alt="[Home]" border=0 align="right"></a>at_c</h1><h3>Synopsis</h3>
<p>
<pre>
template<
typename Sequence
, long n
>
struct at_c
{
typedef <em>unspecified</em> type;
};
</pre>
<p>
<h3>Description</h3>
<p>
Returns a type identical to the <code>n</code>-th element from the beginning of the sequence. <code>at_c<Sequence,n>::type</code> is a shorcut notation for <code>at< Sequence, integral_c<long,n> >::type</code>.
<p>
<h3>Definition</h3>
<p>
<pre>
#include "<a href="../../../../../boost/mpl/at.hpp">boost/mpl/at.hpp</a>"
</pre>
<p>
<h3>Parameters</h3>
<table border="1">
<tr><th> Parameter </th><th> Requirement </th><th> Description </th></tr>
<tr><td><code>Sequence</code></td><td>A model of <a href="../Forward_Sequence.html">Forward Sequence</a></td><td>A sequence being examined. </td></tr>
<tr><td><code>n</code></td><td>An compile-time integral constant</td><td>An offset from the beginning of the sequence that specifies the element to be retrieved. </td></tr>
</table>
<p>
<h3>Expression semantics</h3>
<p>
<table border="1">
<tr><th> Expression </th><th> Expression type </th><th> Precondition </th><th> Semantics </th><th> Postcondition </th></tr>
<tr><td><code>typedef at_c<Sequence,n>::type t;</code></td><td>A type</td><td><code>0 <= n < size<Sequence>::type::value</code></td><td>Equivalent to <code>typedef at< Sequence, integral_c<long,n> >::type t;</code></td><td></td></tr>
</table>
<p>
<h3>Complexity</h3>
<p>
Depends on the implementation of the particular sequence it is applied to. Linear in the worst case, or amortized constant time.
<p>
<h3>Example</h3>
<p>
<pre>
typedef <a href="../Reference/range_c.html">range_c</a><long,10,50> range;
BOOST_STATIC_ASSERT(at_c<range,0>::type::value == 10);
BOOST_STATIC_ASSERT(at_c<range,10>::type::value == 20);
BOOST_STATIC_ASSERT(at_c<range,40>::type::value == 50);
</pre>
<p>
<h3>See also</h3>
<p>
<a href="../Forward_Sequence.html">Forward Sequence</a>, <code><a href="../Reference/at.html">at</a></code>, <code><a href="../Reference/front.html">front</a></code>, <code><a href="../Reference/back.html">back</a></code>
<p><hr>
<a href="../Table_of_Contents.html">Table of Contents</a><br>Last edited October 21, 2002 4:09 am</body></html>
